THURSDAY, July 16 (HealthDay News) -- The incidence of rotavirus infection, a major cause of infant illness in the United States, could be drastically reduced by a better understanding of when and where infections are likely to spread and by the wide use of new vaccines, new research suggests.

A team including scientists from the U.S. Centers for Disease Control and Prevention, the U.S. National Institutes of Health, and elsewhere, noted that rotavirus can cause diarrhea in affected infants and children. The infection is rarely fatal in the United States, but remains a major killer of children in less developed countries.

However, mathematical modeling conducted by the researchers suggests that U.S. rotavirus epidemics are strongly tied to differences in regional birth rates -- for example, incidence is typically higher in the Southwest, where birth rates remain relatively high, compared to the Northeast, where they are relatively low.

According to the researchers, this is important because epidemics are driven by infants who have not previously been infected by the virus. Winter outbreaks of rotavirus could therefore be expected to begin earlier in the Southwest, and only spread later to the Northeast.

The study, published in the July 17 issue of Science, also suggests that epidemics could be better controlled by widespread immunization with two rotavirus vaccines first introduced in 2006. According to the mathematical model, annual epidemics should begin to subside once vaccination rates reach a threshold of 80 percent of children in a given population. Data from 2007-08 seem to validate the model's prediction, the CDC said in an agency news release.

"Rotavirus vaccines have rapidly and dramatically reduced hospitalizations and emergency room visits for gastroenteritis in American children," Umesh D. Parashar, an investigator at the CDC's National Center for Immunization and Respiratory Diseases, said in the release. "This research not only explains the effects of the U.S. rotavirus vaccination program, but also lays the foundation for understanding the tremendous lifesaving benefits of vaccination in the developing world, where more than half a million children die from rotavirus each year."